1. Field of the Invention
The present invention generally relates to image interpolation, and more particularly to a direction-adaptive image upsampling system and method using double interpolation.
2. Description of Related Art
Image upsampling, or image interpolation, is a process of increasing the resolution of an image. It has become an essential technique in many applications, such as image editing software, TV scaler and surveillance systems, and particularly in real-time applications.
Image upsampling may be performed either based on multiple input images or on a single input image. The former one, i.e., the multi-image upsampling, needs long computation time and is thus not suitable for real-time applications.
The latter one, i.e., the single-image upsampling, may be generally classified into three categories: the interpolation-based scheme, the statistic-based scheme and the learning-based scheme. Bilinear and bicubic are commonly used interpolation-based methods, but usually produce zigzagging artifact on the edges. Although further methods have been proposed to solve the zigzagging artifacts, time-consuming edge detection, however, is required. The statistic-based scheme employs edge statistics to reconstruct high-resolution images, but requires several iterations to arrive at a good result. The learning-based scheme predicts high-frequency details by database that requires high computation time.
For the foregoing reasons, a need has arisen to propose a novel interpolation-based scheme that has a simple and robust algorithm with high image quality suitable for real-time applications.